Thursday, September 22, 2011

Extramammary Paget disease is an uncommon malignant neoplasm that occurs in areas with high concentrations of apocrine glands such as the genitoanal area (most common, and usually in women), axilla, eyelids, the oral cavity, and the exernal auditory canal. Patients present with an erythematous, eczematoid, slowly spreading plaque and commonly have interactable pruritus.

As in Paget disease of the nipple, there is intraepithelial (usually intraepidermal) infiltration by neoplastic cells showing glandular differentiation. However, while the origin of the neoplastic cells in Paget disease of the nipple are well-known (in situ or invasive ductal carcinoma in the underlying breast tissue), the origin of neoplastic cells in extramammary Paget disease is somewhat controversial.

The neoplastic cells in extramammary Paget disease are thought to arise from the epidermis (primary form), either from the intraepidermal portions of apocrine gland ducts or from pluripotent keratinocyte stem cells. The secondary form refers to cases where there is an underlying neoplasm in a dermal adnexal gland or a local organ with contiguous epithelium. The word adnexa (appendage) in this context refers to the appendages of skin (hair, arrector pili, sebaceous glands, apocrine or eccrine glands, and nails).